The immune system which is a defense mechanism of a living organism against exogenous or endogenous foreign bodies is formed of a marrow cell group typified by macrophages and neutrophils and a lymphocyte group such as T cells and B cells. These cell groups not only function independently but also act mutually through intercellular direct contact or soluble factors which are collectively called cytokine, thereby maintaining their homeostasis. The defense mechanism is so finely formed so that even the collapse of delicate balance induces a serious morbid state.
Such collapse of an immunocyte control mechanism triggers the production of autoantibodies or induces excessive immunoreaction, which is thought to cause collagen disease, systemic lupus erythematosus and various allergic diseases. It is known that in AIDS (acquired immunodeficiency syndrome), the infection of T cells with HIV causes decay of the immune system and this decay proceeds further. In addition, chronic diseases caused by diabetes or viruses or the development of a morbid state of a cancer also occurs partly because of the loss in immune balance.
In recent years, cytokine production suppressants such as cyclosporin and FK506, which have already been known as a rejection suppressant upon organ transplantation, have been used for the treatment of the above-described diseases. Besides, steroidal anti-inflammatory agents having inhibitory effects against cytokine production have been used for autoimmune diseases such as allergy, atopy and rheumatism and bronchial asthma and have achieved therapeutic effects to some extent.
It is well known that the immune system is indispensable for the temporary defense mechanism of a host and under the immunodeficient conditions induced by the administration of an immunosuppressant or a carcinostatic agent, the host is easily attacked by infectious diseases. At present, a medicament, for example, an immunosuppressant or steroidal anti-inflammatory agent, for suppressing the production of various cytokines cannot be applied freely to an autoimmune disease and it is limited in the administration method or drug holidays. For the treatment of the above diseases related to the immune system, there is accordingly a demand for the development of an immunoregulator with high specificity which acts on only a specific immune phenomenon.
An object of the present invention is therefore to provide a potential immunoregulator with high specificity and high safety which can suppress the excessive production of a specific cytokine in various immune diseases.